The present invention relates generally to temperature indicators, and more particularly, to an apparatus and method to extend and retract a temperature indictor stick.
Temperature indicators are well known in the welding, metal fabrication, and heat treatment industries. Such products are capable of determining surface temperatures during welding and metal fabrication processes. The products have also found use in heat-treatment processes, and can determine operating temperatures of mechanical, hydraulic, and electrical systems and components, such as transformers and motors.
Initially, temperature sensing was conducted by sprinkling a few granules of a known compound on an object. When the granules melted, the desired temperature was achieved. Later, pellets were introduced to make marks similar to a chalk mark on a surface of the object rather than observing the entire pellet melt. Further improvements led from a pellet to a chalk stick, which is protected in a housing that includes an adjustable holder for positioning the temperature indicator stick relative to the housing.
One known temperature indicator includes a housing having a rimmed end and a flanged end. A temperature indicator stick is inserted into the housing through the flanged end and prevented from leaving the housing by the rimmed end. The stick also has an outer casing or holder that is threaded into the housing and encloses the flanges.
The outer casing is tapered to constrict the flanges and lock the temperature indicator stick in a fixed position with a portion of the temperature indicator stick extending from the housing. Normal use of the temperature indicator stick by an operator causes a decrease in the portion of the temperature indicator stick extending from the housing, and eventually necessitates further advancement of the temperature indicator stick by the operator for continued temperature detection.
Problems exist with the current state of the art of temperature indicators. Existing holders for temperature indicators are not satisfactory. Such holders are often limited in their ability to fix the temperature indicator stick in position. When the stick is used by an operator, pressure exerted on the end of the stick during marking causes the stick to retract into the housing. Generally, the operator must unscrew the outer casing, reposition the temperature indicator stick, and then retighten the outer casing to continue marking objects. Other known methods of marking an object such as using the temperature indicator stick without a housing and holder are also unsatisfactory. Since the temperature indicator stick is fragile and clutched by the operator using a heat-resistant glove, the temperature indicator stick can be easily broken resulting in material waste. Furthermore, inscriptions on housings are useful to provide a particular temperature rating of the temperature indicator stick, which is critical to properly identifying the surface or operating temperatures of the object under evaluation.
There is a need for an apparatus and method capable of fixing a temperature indicator stick in position during the marking of objects for temperature detection. It would therefore be desirable to have a more efficient temperature indicator than current indicator configurations by coupling a collet having a threaded portion to a housing such that threads of the collet engage a temperature indicator stick.